Carburetor for internal combustion engines

ABSTRACT

A carburetor for internal combustion engines with a screen in the fuel-outlet including portion of the suction pipe for the combustion air, located in front of the throttle valve and in an asymmetrical relation to a plane including the axes of the suction pipe and the throttle valve, said screen forming at the most an acute angle with the suction pipe axis and forming flow control surfaces for the combustion air in the suction pipe.

United States Patent 1 Hammerschmied 1 May 13, 1975 1 CARBURETOR FOR INTERNAL COMBUSTION ENGINES [76] Inventor: Georg Hammerschmied,

Leonhardstrasse 52, Graz, Austria [22] Filed: Jan. 10, 1973 [21] Appl. No.: 322,535

[30] Foreign Application Priority Data Jan, 14, 1972 Austria 343/72 Oct. 25, 1972 Austria 9135/72 [52] US. Cl. 261/78 R; 261/D1G. 39 [51) Int. Cl. F02m 19/08 {58] Field of Search 261/78 R, 76, DIG. 39, 261/41 R [56] References Cited UNITED STATES PATENTS 1,123,027 12/1914 Simonsen 261/D1G. 39 1,246,727 11/1917 Donning 1111 26l/DlG. 39 1,453,490 5/1923 Bessom 261/DlG, 39 2,126,132 8/1938 Paasche.... 26l/DIG. 39

2,375,160 5/1945 Woods 261/78 R 2,554,660 5/1951 Car1son..... 261/41 R 2,980,408 4/1961 Marsee 1 261/41 R 2,991,052 7/1961 Carlson et a1 261/D1G. 39

3,168,599 2/1965 Marsee et a1. 261/D1G. 39

3,326,539 6/1967 Phipps i 261/DlG, 39 3,346,246 10/1967 Loet et a1. i. 261/D|G l1 FOREIGN PATENTS OR APPLICATIONS 212,735 3/1924 United Kingdom 26l/D1G. 39 521,074 7/1953 Belgium 261/76 824,378 11/1937 France 261/78 R 875,699 9/1942 France 26l/D1G. 39

602,404 3/1926 France 26l/DlG, 39 1,010,806 6/1952 France 261/78 R 368,608 3/1932 United Kingdom 261/78 R Primary Examiner-Tim R. Miles Attorney, Agent, or FirmWatson, Cole, Grindle & Watson [57} ABSTRACT A carburetor for internal combustion engines with a screen in the fuel-outlet including portion of the suction pipe for the combustion air, located in front of the throttle valve and in an asymmetrical relation to a plane including the axes of the suction pipe and the throttle valve, said screen forming at the most an acute angle with the suction pipe axis and forming flow control surfaces for the combustion air in the suction pipe 7 Claims, 7 Drawing Figures gill/[1111".

PATENIEB MAY 1 31975 SBEEI 2 RF 2 vikm/hl CARBURETOR FOR INTERNAL COMBUSTION ENGINES The invention relates to a carburetor for internal combustion engines comprising flow control surfaces located in the air intake.

Particularly as a result of the ever increasing motorization and the resulting increase of the percentage of harmful exhaust gases contained in the air. the problems involved in environmental protection are steadily gaining importance. Consequently, efforts are being made all over the world with a view to reducing the percentage of harmful components of the exhaust gases of internal combustion engines, particularly, the carbon monoxide content but also the nitrogen content, as far as possible.

Thus far. this problem has been attacked from various angles. in addition to the development of highgrade fuels facilitating and improving the combustion process proper, exhaust gas decontamination equipment connected to the exhaust system for the purpose of retaining and/or extinguishing the poisonous components of exhaust gases play an important part in engine designers endeavors to attain the highest possible degree of environmental protection. The reasons behind the apparent failure of exhaust gas decontamination equipment to attain general acceptance are in addition to its high cost also the considerable space required by them and the absolute need for attendance. Therefore, this type of equipment is hardly suitable for motor vehicles of the lower and medium bracketsv The quality of combustion in the cylinders of an in ternal combustion engine is largely dependent upon the quality of the preparation of the fuel-andair mixture. Where engines feature external mixture formation it is. therefore, necessary to provide for the most uniform mixture formation possible in all load areas in the carburetor area in addition to a design of the inlet port system ensuring optimal flow conditions.

A great number of special types of carburetors are already known to achieve a reduction of the fuel consumption and/or an increase in engine performance by installing appropriate units in the suction pipe. A few of these known carburetors are provided with flow control surfaces similar to guide vanes and causing a flow rotating about the axis of the suction pipe. Other conventional types of carburetors feature hollow bodies with a multitude of apertures, installed in the crosssection of the suction pipe and largely of a conical or paraboloid shape, by means of which a greater mixing action is to be attained in the portions of the suction port behind. For similar purposes various types of ring nozzles arranged concentrically in the suction pipe have been devised. as well as tongues radially extending approximately as far as the center of the cross-section producing turbulence in the fueLand-air mixture drawn in.

A drawback of all of these known design resides in the fact that they fail to contribute essentially to a re duction of the noxious components of exhaust gases while the inserts to be provided generally produce a high resistance to flow in the intake duct.

Moreover, the often very expensive inserts tend to increase the production cost of the carburetor to a considerable extent.

It is the purpose ofthe invention to improve a carburetor for internal combustion engines of the type hereabove described in such a manner as to attain as far as possible, the ideal condition where complete combustion is achieved at minimum temperatures by appropriately controlling the combustion process over the entire load area of the engine at a minimum of structural and financial expense. According to the invention, this problem is solved in a surprisingly simple manner by providing flow control surfaces at at least one screen located in the suction pipe portion in front of the throttle valve as viewed in the main direction ofthe air flow, said screen being arranged asymmetrically in relation to a plane including the suction pipe axis and the axis of the throttle valve and forming at the most an acute angle with the axis of the suction pipe.

Practical experience has shown that by means of this most practicable measure. actually suitable for all types of carburetors. the percentage of carbon monoxide in the exhaust gas is reduced to a fraction of the customary value, particularly in the idling or noload zone where the percentage of this type of exhaust gases is still measurable. At the same time, the percentage of nitrogens contained in the exhaust gases can be reduced by lowering the combustion temperature. such as for example. by reducing the spark advance or the compression.

Although the particular flow conditions responsible for this surprising effect have not as yet been fully investigated into, there can be no doubt whatsover that as a result of the arrangement of a screen comprising or forming flow control surfaces certain flow conditions are produced in the aforesaid area of the suction pipe which ensure a better fuel distribution over the pipe cross-section on the one hand and inhibit the for mation of countenflows liable to obstruct and possibly. even arresting the discharge from the fuel outlet of the carburetor on the other hand.

The screen according to the invention is provided for the purpose of permitting the supply of fuel via the outlet already in the lower speed range, that is with the throttle valve still almost closed. lt is thus possible to limit the effect of the idling setscrew and occasionally, in certain types of carburetors. no idling setscrew is required at all. Therefore. by means of the screen, the response of the outlet which, as pointed out above, is impaired by counter-flows with the throttle valve largely closed, is intensified. provided the flow is already directed in the lower working range of the carburetor.

By means of the screen located in a marginal area of uncertain flow conditions the carburetor according to the invention is divided into areas of varying flow behavior, the advantage of which resides in the fact that they produce a sort of inoperative flow in front of the outlet.

According to a preferred embodiment of the invention the screen is provided with grid-like perforations. With a screen which is perforated grid-fashion the apertures of the screen inhibit any counter-flow by producing a flow component acting in the direction of the main current. A braking action is produced at the outside of the screen whereas the air current is hardly im paired on the wall ofthe smooth suction pipe The flow differences in connection with the proper weight of the fuel thus result in a deflection of the fuel in relation to the direction of the main current in the suction piper ln addition, the grid-like perforated screen acts in the fashion of a deflector. Consequently, the fuel is more finely divided on the one hand and removed from the fuel outlet also in the lower speed range and incorporated in the existing marginal flow on the other hand.

According to a particularly simple embodiment of the invention the screen is made from expanded metal which is not only inexpensive but available in all commercial types and mesh sizes.

According to another feature of the invention. the grid-like perforations of the screen are designed as ducts forming preferably acute angles with the direc' tion ofthe main current in the suction pipe. This design encourages the formation and uniform distribution of a fine fuel mist in the area around the fuel outlet.

In the latter event particularly effective results have been achieved by inclining the ducts formed by the per forations of the screen according to the invention to wards the center of the suction pipe.

According to another embodiment of the invention the screen can be made from sheet metal and be pro vided with a sieve-like perforation.

A particularly simple design is achieved according to the invention by providing a plate-shaped screen extending preferably only over the central portion of the cross-section of the suction pipe. Such a screen can be produced at low cost by a simple cutting or punching process from sheet metal, expanded metal or the like.

According to another embodiment of the invention the screen is either cylinder-shaped or designed as part of a cylinder. The most advantageous radius and the other dimensions of the screen depend on the size and design of the carburetor and are preferably determined by trial and error.

However, according to the invention the screen may also have the shape of a generally cylindrical surface whose generating lines form at the most acute angles with the axis of the suction pipe. This makes it possible to adapt the shape of the screen to the design of the carburetor so as to suit any given special flow condi tions.

According to a particularly effective embodiment of the invention the screen is arranged symmetrically in relation to a plane which is normal in relation to the throttle valve axis and includes the axis of the suction pipe. This arrangement takes the particular flow condi tions prevailing when the throttle valve is only slightly opened into account.

Favorable results are achieved according to another embodiment of the invention by arranging the screen on the same side of the suction pipe that portion of the throttle valve which opens in the direction of the main current. Experience has shown the effect according to the invention to be achievable in full already with the throttle valve only very slightly opened.

In connection with carburetors comprising an accelerator nozzle terminating in the suction pipe it is advisable according to another feature of the invention to locate the screen in the area between the accelerator nozzle and the fuel outlet.

According to a preferred embodiment of the invention the screen should be directly attached to the car buretor element forming the fuel outlet. With this arrangment, flow components directed in transverse relation to the direction of the main current prevail in the area of the fuel outlet also in the event of the throughput through the suction pipe being throttle-d to a considerable extent.

According to the invention the fuel outlet arm of carburetors comprising a fuel outlet in the shape ofan arm (ill radially protruding into the suction pipe presents :1 lat eral truncation to which the screen is attached in spaced relation. Thus the correct location of the screen is determined in a simple manner.

According to another special embodiment of the invention the screen is concave in relation to the axis of the suction pipe and surrounds the fuel outlet at least in part. The most advantageous bend and the peripheral area over which this screen extends. as well as its height and its inclination. if any. in relation to the axis of the suction pipe are determined preferably by trial and error.

According to another variant of the carburetor ac cording to the invention the screen is convex in relation to the axis of the suction pipe and preferably adjoins the inner wall of the suction pipe with its lateral rims. This design of the screen may be advantageous, for example. if a certain amount of asymmetry of the main current prevails in the suction pipe proper.

Another embodiment ofthe invention provides for a carburetor whose screen extends over the entire width of the suction pipe.

Finally. according to a special feature of the invention an additional screen is provided in front of the fuel outlet connected with the main nozzle in the suction pipe. Said additional screen is designed as a body open in the axial direction of the suction pipe and having apertures on its peripheral surface. This preferably hollow body is located in spaced relation to the inner wall of the suction pipe extending over at least part of its height. That part of the body faces the fuel outlet. the apertures of the body presenting directions forming angles with the main direction of the air current and with the main axis of the suction pipe. In this type of carburetor an additional flow effect will present itself consisting in the formation of a counterflow area in opposition to the main direction of the air current and surrounding the central main air current shell-fashion in the area around the additional screen. At the same time. the fuel mist is drawn back from its origin in the area around the fuel outlet or around the idling nozzle as far as the area of the additional screen and reintroduced in the central main air current via the apertures of the latter. Intense preparation of the fuel-and=air mixture occurs already in this area. as a result of which the formation of a fuel film in the suction system is largely avoided and combustion in the cylinders of the engine concerned is more closely approximated to the ideal condition.

Further details of the invention will become apparent from the following description of several embodiments of the invention with reference to the accompanying drawings in which FIG. 1 shows a partially axial sectional view of a car buretor restricted to such areas as are essential for the understanding of the scope of the invention.

FIG. 2 is a top plan view of the lower portion of the carburetor on line llll of FIG. I.

FIGS. 3 through 5 are variants of the carburctor according to the invention in an illustration correspond ing to FIG, 2,

FIG. 6 is a diagram showing the percentage of carbon monoxide contained in the exhaust gases of two different types of carburetors. and

FIG. 7 is a partially axial sectional view of yet another variant of the carburetor according to the invention corresponding to FIG. I.

The carburetor comprises a cover 2 screwed to the body 1 of the carburetor with the interposition of a gasket 3. The float chamber is designated by reference number 4, the float by 5 and the fuel inlet line leading to the float chamber by reference number 6. The fuel outlet arm 8 with outlet 9 connected with the main nozzle (not shown) of the carburetor protrudes into the suction pipe 7 of the body of the carburetor. The outlet 9 is arranged in the suction pipe 7 approximately in central relation to same and terminates in the direction of the main air current indicated by the arrow 10'. The idling nozzle 12 of the carburetor is screwed into the connecting bore 1] emerging from the main nozzle and laterally offset towards the float chamber 4.

ln the portion of the suction pipe 7 located in the cover 2 the air flap [3 shown in its opened position is rotatably supported. In addition, the inclined air-vent pipe 14 of the float chamber 4 protrudes into the suction pipe 7. The accelerator nozzle 15 of the carburetor terminates on the opposite side of the suction pipe 7.

In the portion of the suction pipe located in the body of the carburetor, the throttle valve 16 of the carburetor is supported so as to be rotatable about the axis 16'. In the portion of the suction pipe located in front of the throttle valve 16 a screen 17 perforated grid-fashion is provided on the side of that part 16" of the throttle valve 16 which opens in the direction of the main current. Said screen 17 is made of expanded metal for example and designed asymmetrically in relation to a plane 18 including the axis of the suction pipe 10 and the axis of the throttle valve 16. In the carburetor according to the invention illustrated in FIGS. 1 and 2 this screen presents a generally cylindrical surface bent C- fashion as viewed from above. The screen 17 is laterally attached to the fuel outlet arm 8.

As appears from FIG. 1, the ducts formed by the gridlike perforations 20 of the screen 17 form acute angles with the main axis 10 of the suction pipe 7 and are inclined towards the middle of the suction pipe 7. When the screen 17 is designed as shown in FIGS. 1 and 2, it partially comprises the outlet 9 of the fuel outlet arm 8 and is located symmetrically in relation to a plane 19 including the axis 10 of the suction pipe 7 and in perpendicular relation to the plane 18.

As shown in FIGS. 3 thru 5, depending on the carburetor design and the basic flow conditions in the suction pipe 7, the screen can be of a different shape than the one hereabove described. For example, according to FIG. 3 the screen is designed as a flat rectangular plate attached directly to the flattened flange 21 of the fuel outlet arm 8 preferably in a slightly spaced relation, for example with the interposition of a spacer 24 or an intermediate piece presenting a groove underneath and extending only over part of the width of the suction pipe 7. However, said distance must be sufficiently large to preclude any overflow of fuel from the outlet to the screen.

In the embodiment shown in FIG. 4 the grid-like perforated screen 17 presents a concave curvature in relation to the axis 10 of the suction pipe and extends over the entire width of the suction pipe 7.

The screen 17 illustrated in H6. 5 has an essentially C-shaped cross-section. the open side of the C-facing the inner wall 22 of the suction pipe 7. With its lateral rims. the screen 17 directly adjoins the inner wall 22 of the suction pipe 7.

A common feature of all types of grid-like perforated screens 17 is their surprisingly considerable influence upon the formation of a finely divided fuel-and-air mixture and consequently, upon the progress of combustion in the cylinders of the engine concerned. The best possible combustion progress is achieved practically in the entire operating range of the engine, resulting in an astounding reduction of the carbon monoxide content of the exhaust gases produced. This is particularly noticeable in the idling range and at low speed. The diagram shown in FIG. 6 clearly illustrates the effect of the equipment of a carburetor according to the invention upon the carbon monoxide content of the exhaust gases.

FIG. 6 indicates the carbon monoxide content as expressed in percentages of the exhaust gases ofa serially produced automotive Otto engine over the speed range v in kilometers per hour. Curve A represents the result of an examination of the waste gases of an engine equipped with an ordinary carburetor, whereas curve B illustrates the result of measurements carried out with the same carburetor equipped according to the present invention. Each of the two curves represents the average of two series of readings of which one was taken at rising and the other at diminishing speeds.

As shown in the diagram, the percentage of carbon monoxide in the exhaust gases of a serially produced carburetor according to curve A in the low speed range, of almost 6 per cent. by volume is extremely high and diminishes only over the customary speed range, rising again as the speed increases. In the light of environmental protection the carbon monoxide values, particularly in the idling range, must be considered to be highly excessive.

On the other hand, as revealed by curve B, the percentage of carbon monoxide with a carburetor accord ing to the present invention represents only a small fraction of the figures for serially produced carburetors. Particularly noticeable is the negligible carbon monoxide content in the idling range which is highly important for environmental protection, since experience goes to show that particularly high carbon monoxide concentrations usually occur where due to particular traffic conditions a large number of engines are running idle.

In the variants ofa carburetor according to the invention as hereabove described, one screen 17 only is provided in the proximity of the fuel outlet 9. FIG. 7 illustrates another type of carburetor according to the invention comprising an additional screen 17' in the area in front of the air flap 13. This additional screen 17' is located within the air scoop 26 attached to the inlet connection 25 of the carburetor cover 2, which is usually part of the air filter housing of the internal combustion engine and only partially shown in the drawing.

The screen 17' comprises two coaxially arranged truncated hollow bodies 27 and 28 having apertures 20 like the screen 17 providing ducts forming an acute angle with the main axis 10' of the suction pipe 7. The two hollow bodies 27 and 28 are held in place by means ofa support 29 engaging in recesses 30 at the upper rim of the inlet connection 25. The screen 17 can be provided with an eccentrically arranged pipe 31 extending as far as close to the closed air flap l3 and occasionally carrying a flange 32 at its air flap end. The pipe 31 has a lateral recess 33 into which the free extremity of the air-vent pipe l4 protrudes.

As indicated by arrows in FIG. 7, the additional screen 17' leads to the formation of a definite counterflow area in the proximity of the wall of the suction pipe 7. In the counter-flow area the fuel mist is reconducted from the area of the idling nozzle 12 to the screen 17' and again mixed with the central main air current via apertures 20 of the hollow bodies 27 and 28. The improvement of the preparation of the fueland-air mixture due to the presence of the screen 17 is thus further increased.

The invention is not restricted to the embodiments hereabove described and as shown in the drawings but permits of a great number of variants of carburetor design as well as with regard to the shape and arrangement of the screen and the shape of the apertures on the screen. Such embodiments where the screen has no apertures at all or only a small number of apertures, are also well within the scope of the present invention.

I claim:

1. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the suction pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having grid-like perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe, and said fuel outlet arm protruding radially into the suction pipe and presenting a laterally flattened portion to which said screen is attached in spaced relation.

2. A carburetor according to claim 1, wherein said screen is made of expanded metal.

3. A carburetor according to claim I, wherein said grid-like perforations of the screen provide ducts forming angles with the direction of the combustion air flow in the suction pipe.

4. A carburetor according to claim 3, wherein said ducts form acute angles with the direction of flow of the combustion air.

5. A carburetor according to claim 3, wherein said ducts are inclined towards the center of the suction pipe respective to the direction of suction air.

6. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the suction pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having grid-like perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen comprising lateral rims by means of which the screen rests on the inner surface of the suction pipe, and said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe.

7. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the second pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having grid-like perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe, an additional screen arranged in the first suction pipe portion in front of the fuel outlet, said additional screen being designed as a hollow body open in the direction of the suction pipe axis with apertures on its peripheral surface and being arranged over at least part of its height in spaced relation to the inner wall of the suction pipe, said spaced portion of the hollow body facing said fuel outlet, and said apertures of the hollow body presenting directions forming angles with the direction of the air flow and with the axis of said suction pipe.

l I i 

1. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the suction pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having gridlike perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe, and said fuel outlet arm protruding radially into the suction pipe and presenting a laterally flattened portiOn to which said screen is attached in spaced relation.
 2. A carburetor according to claim 1, wherein said screen is made of expanded metal.
 3. A carburetor according to claim 1, wherein said grid-like perforations of the screen provide ducts forming angles with the direction of the combustion air flow in the suction pipe.
 4. A carburetor according to claim 3, wherein said ducts form acute angles with the direction of flow of the combustion air.
 5. A carburetor according to claim 3, wherein said ducts are inclined towards the center of the suction pipe respective to the direction of suction air.
 6. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the suction pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having grid-like perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen comprising lateral rims by means of which the screen rests on the inner surface of the suction pipe, and said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe.
 7. A carburetor for internal combustion engines comprising a suction pipe for combustion air having a first suction pipe portion and a second suction pipe portion adjoining the former in the direction of the combustion air flow, a throttle valve located in the second suction pipe portion and rotatable around an axis extending in transverse relation to the axis of the second pipe, a fuel outlet arm arranged in said first suction pipe portion and presenting a fuel outlet, a screen having grid-like perforations and arranged in said first suction pipe portion adjacent the fuel outlet arm, said screen forming at the most an acute angle with the axis of the suction pipe and providing flow control surfaces for the combustion air in the suction pipe, an additional screen arranged in the first suction pipe portion in front of the fuel outlet, said additional screen being designed as a hollow body open in the direction of the suction pipe axis with apertures on its peripheral surface and being arranged over at least part of its height in spaced relation to the inner wall of the suction pipe, said spaced portion of the hollow body facing said fuel outlet, and said apertures of the hollow body presenting directions forming angles with the direction of the air flow and with the axis of said suction pipe. 